The invention relates generally to catheters, and more particularly to a catheter having a steerable distal-end region with a shaft support system for resisting axial compressive loads.
The heart beat in a healthy human is controlled by the sinoatrial node (xe2x80x9cS-A nodexe2x80x9d) located in the wall of the right atrium. The S-A node generates electrical signal potentials that are transmitted through pathways of conductive heart tissue in the atrium to the atrioventricular node (xe2x80x9cA-V nodexe2x80x9d) which in turn transmits the electrical signals throughout the ventricle by means of the His and Purkinje conductive tissues. Improper growth of, or damage to, the conductive tissue in the heart can interfere with the passage of regular electrical signals from the S-A and A-V nodes. Electrical signal irregularities resulting from such interference can disturb the normal rhythm of the heart and cause an abnormal rhythmic condition referred to as xe2x80x9ccardiac arrhythmia.xe2x80x9d
While there are different treatments for cardiac arrhythmia, including the application of anti-arrhythmia drugs, in many cases ablation of the damaged tissue can restore the correct operation of the heart. Such ablation can be performed by percutaneous ablation, a procedure in which a catheter is percutaneously introduced into the patient and directed through an artery or vein to the atrium or ventricle of the heart to perform single or multiple diagnostic, therapeutic, and/or surgical procedures. In such case, an ablation procedure is used to destroy the tissue causing the arrhythmia in an attempt to remove the electrical signal irregularities or create a conductive tissue block to restore normal heart beat or at least an improved heart beat. Successful ablation of the conductive tissue at the arrhythmia initiation site usually terminates the arrhythmia or at least moderates the heart rhythm to acceptable levels. A widely accepted treatment for arrhythmia involves the application of RF energy to the conductive tissue.
In the case of atrial fibrillation (xe2x80x9cAFxe2x80x9d), a procedure published by Cox et al. and known as the xe2x80x9cMaze procedurexe2x80x9d involves continuous atrial incisions to prevent atrial reentry and to allow sinus impulses to activate the entire myocardium. While this procedure has been found to be successful, it involves an intensely invasive approach. It is more desirable to accomplish the same result as the Maze procedure by use of a less invasive approach, such as through the use of an appropriate electrophysiological (xe2x80x9cEPxe2x80x9d) catheter system.
One such EP catheter system, as disclosed in U.S. Pat. Nos. 6,059,778 and 6,096,036, includes a plurality of spaced apart band electrodes located at the distal end of the catheter and arranged in a linear array. The band electrodes are positioned proximal heart tissue. RF energy is applied through the electrodes to the heart tissue to produce a series of long linear lesions similar to those produced by the Maze procedure. The catheters currently used for this procedure are typically flexible at the distal end, and the profile at the distal end is adjustable. However, when using such catheters, it is often difficult to conform the distal-end profile to some of the irregular topographies of the interior cavities of the heart. In other instances, it is difficult for a multi-electrode catheter that is designed to produce long linear lesions to access and ablate tissue in regions that require short linear lesions, such as the so-called isthmus region that runs from the tricuspid annulus to the eustachian ridge. Ablation of tissue in this region, and other regions non-conducive to the placement of multi-electrode, long, linear-lesion ablation catheters within them, is best accomplished by delivering RF energy to a tip electrode to produce localized spot lesions or if longer lesions are required, by energizing the tip while it is moved across the tissue.
Other catheters for producing spot lesions or tip-drag lesions typically include a tip ablation electrode and a plurality of mapping band electrodes positioned at the distal end of the catheter. The catheters are steerable in that they are configured to allow the profile of the distal end of the catheter to be manipulated from a location outside the patient""s body. Steerable catheters that produce multiple deflection profiles of their distal ends provide a broader range of steerability. However, known steerable catheters, such as that disclosed in U.S. Pat. No. 5,195,968, have steering tendons attached to a ribbon at or near the longitudinal centerline of the catheter. Because of the relatively short distance between the tendon attachment point and the ribbon that resides along the centerline of the catheter sheath, a force applied to the tendon results in a relatively small bending moment for deflecting the distal tip. The ribbon/tendon assembly is typically provided clearance to allow the tendon to become substantially displaced from the centerline as deflection progresses, thereby enlarging the moment arm and consequently increasing the applied bending moment. Unfortunately, this requires such designs to include additional lumen space, translating into larger catheter diameters. Larger diameter catheters are undesirable due to the increased trauma they inflict on a patient. Further, as the tendon displaces to the extent that it contacts the catheter wall, the associated friction may necessitate greater exertion to further deflect the distal tip. Lessening the amount of force required to deflect the distal tip of a catheter by actions outside the catheter is desired in that the catheter tip can more easily be deflected and placed in the correct location within a patient.
In some catheters that have a ribbon within the distal-end region and a steering tendon affixed to the sheath at a point proximal the distal tip within the distal-end region, undesirable deformation of the sheath can occur when the steering tendon is axially displaced in the proximal direction. More specifically, as the steering tendon is axially displaced in the proximal direction, the portion of the sheath in the distal-end region proximal the attachment point compresses, thus causing the sheath to wrinkle, and the portion of the sheath distal the attachment point stretches. Such deformation of the sheath can lead to fluid ingress beneath the catheter""s band electrodes or can cause damage to internal wires or mechanical components.
Hence, those skilled in the art have identified a need for a tip-electrode, ablation catheter with a steerable distal-end region that resists deformation even after repeated steering. The present invention fulfills these needs and others.
Briefly, and in general terms, the present invention is directed to a catheter with a steerable distal-end region and a shaft support system for resisting axial compressive loads.
In a first aspect, the invention relates to a catheter that includes a sheath having a proximal region, a distal-end region, and a longitudinal centerline. The catheter also includes at least one steering tendon that is housed within the sheath. The at least one steering tendon has a first end that is attached to the distal-end region of the sheath, and a second end that is located at the proximal region of the sheath. Movement of the at least one steering tendon in a proximal direction causes the sheath distal-end region to deflect. The catheter also includes a support system having a proximal end, a distal end and a lumen there between. The support system is sized to fit within the distal-end region of the sheath and is configured to deflect laterally relative to the centerline and to resist axial compression along the centerline.
In a detailed aspect of the invention, the support system includes a helical coil that defines the lumen and at least one strut that is secured to one side of the coil along the length of the coil. In another aspect, the support system includes a pair of struts secured to diametrically opposite sides of the coil. In a further aspect, the support system is formed of a resiliently deformable, shape-memory material. In another detailed facet of the invention, the support system includes a linear array of hollow rings that defines the lumen, and at least one strut that is secured to one side of each of the rings. In a further facet, the support system includes a pair of struts that are secured to diametrically opposite sides of each of the rings. In another detailed aspect of the invention, the support system includes a substantially tubular member with an array of notches. In a more detailed aspect, the notches are diametrically opposite and offset from each other. In another detailed facet of the invention, the catheter includes a ribbon isolation sleeve that has a proximal end attached to the distal-end of the support system. In a further facet, the ribbon isolation sleeve is formed of a resiliently deformable material. In a more detailed facet the ribbon isolation sleeve includes a wire coil embedded within the material. In yet another detailed aspect of the invention, the first end of the at least one steering tendon is attached at a location offset from the centerline of the sheath.
In a second aspect, the invention relates to a catheter that includes a sheath having a proximal region and a distal-end region. The catheter also includes a first steering tendon that is housed within the sheath. The first steering tendon has a first end that is attached to the distal-end region at a point proximate an inner surface of the sheath, and a second end that exits a proximal end of the sheath. Movement of the first steering tendon in a proximal direction causes the sheath distal-end region to deflect. The catheter also includes a second steering tendon that is housed within the sheath. The second steering tendon has a first end and a second end. The first end of the second steering tendon is attached to the distal-end region at a point proximate the inner surface of the sheath and proximal the attachment point of the first steering tendon. The second end of the second steering tendon has a second end that exits the proximal end of the sheath. Movement of the second steering tendon in the proximal direction causes the sheath distal-end region to deflect. The catheter also includes a compression cage that has a proximal end, a distal end and a lumen there between. The compression cage is sized to fit within the distal-end region of the sheath and is configured to deflect laterally and to support an axial load.
In a detailed aspect of the invention, the first end of the second steering tendon is coupled to the compression cage. In a more detailed aspect, the first end of the second steering tendon attaches to a distal portion of the compression cage. In another detailed facet of the invention, the catheter also includes an anchor band that is attached to the distal end of the compression cage. In another facet, the first end of the second steering tendon is attached to the anchor band. In another detailed aspect of the invention, the catheter also includes a torque transfer system that is housed within the compression cage and is adapted to transfer torsional forces from the proximal region of the sheath to the distal-end region of the sheath. In a more detailed aspect, the torque transfer system includes an eyelet that is secured at the distal end of the proximal region of the sheath and the proximal end of the compression cage is secured to the eyelet. In another detailed aspect, the torque transfer system further includes a ribbon that is housed within the compression cage and is configured to deflect therewith. The ribbon has a first end that is secured within the eyelet and a second end that is attached to the distal-end region of the sheath. In a further detailed aspect, the ribbon is positioned along the centerline of the distal-end region of the sheath. In an additional aspect, the ribbon is formed of a resiliently deformable, shape-memory material. In a still further aspect, the ribbon has a substantially rectangular cross-section. In yet another aspect, the compression cage and the ribbon are each adapted to deflect in a direction, and the compression cage further includes a ribbon locator that is adapted to align the deflecting direction of the compression cage with the deflecting direction of the ribbon.
In a third aspect, the invention relates to a catheter for use with biological tissue that includes a sheath having a proximal region and a distal-end region. The catheter also includes at least one electrode that is located in the distal-end region for transferring energy to the biological tissue. The catheter further includes a first steering tendon that is housed within the sheath. The first steering tendon has a first end that is attached to the distal-end region at a point proximate an inner surface of the sheath, and a second end that exits a proximal end of the sheath. Movement of the first steering tendon in a proximal direction causes the sheath distal-end region to deflect. The catheter also has a second steering tendon that is housed within the sheath. The second steering tendon has a first end and a second end. The first end of the second steering tendon is attached to the distal-end region at a point proximate the inner surface of the sheath and proximal the attachment point of the first steering tendon. The second end of the second steering tendon exits the proximal end of the sheath. Movement of the second steering tendon in the proximal direction causes the sheath distal-end region to deflect. The catheter also includes a compression cage that has a proximal end, a distal end and a lumen there between. The compression cage is sized to fit within the distal-end region of the sheath and is configured to deflect laterally therewith and to resist axial compression. The catheter further includes a torque transfer system that is housed within the compression cage and is adapted to transfer torsional forces from the proximal region of the sheath to the distal-end region of the sheath.
In a detailed aspect of the invention, the first steering tendon is secured within a distal tip of the sheath. In another aspect, the at least one electrode includes a tip electrode that is located at the distal end of the sheath, and the first steering tendon is secured within the tip electrode. In another detailed facet of the invention, the compression cage includes a helical coil that defines the lumen, and at least one strut that is secured to one side of the coil along the length of the coil. In a more detailed facet, the catheter also includes an anchor band that has a proximal end and a distal end with a central lumen there between. The anchor band is housed within the distal-end region, and the proximal end of the anchor band is attached to the distal end of the compression cage. In a further facet, the first end of the second steering tendon is attached to the anchor band.
These and other aspects and advantages of the invention will become apparent from the following detailed description and the accompanying drawings, which illustrate by way of example the features of the invention.